Customized patient-specific tibial cutting blocks

ABSTRACT

A number of orthopaedic surgical instruments are disclosed. A method, apparatus, and system for fabricating such instruments are also disclosed.

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Ser. No. 61/308,134, entitled “CustomizedPatient-Specific Tibial Cutting Blocks,” which was filed on Feb. 25,2010 by Luke Aram et al., and is continuation-in-part application ofco-pending U.S. Utility patent application Ser. No. 12/240,990 entitled“Customized Patient-Specific Instrumentation for Use In OrthopaedicSurgical Procedures,” which was filed by Luke Aram et al. (AttorneyDocket No. 265280-207007, DEP-6047USNP) on Sep. 29, 2008 which claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Patent ApplicationSer. No. 60/976,447 entitled “Method and Apparatus for FabricatingCustomized Patent Instrumentation,” which was filed on Sep. 30, 2007 byDan Auger et al.; U.S. Provisional Patent Application Ser. No.60/976,448 entitled “Adjustable Customized Patient-Specific OrthopaedicSurgical Instrumentation,” which was filed on Sep. 30, 2007 by Luke Aramet al.; U.S. Provisional Patent Application Ser. No. 60/976,451 entitled“Customized Patient-Specific Instrumentation For Use In OrthopaedicSurgical Procedures,” which was filed on Sep. 30, 2007 by Jeff Roose etal.; U.S. Provisional Patent Application Ser. No. 60/976,444 entitled“Method and Apparatus for Patient-Specific Positioning of OrthopaedicSurgical Instrumentation,” which was filed on Sep. 30, 2007 by Luke Aramet al.; and U.S. Provisional Patent Application Ser. No. 60/976,446entitled “Method and Apparatus for Aligning Customized Patient-SpecificOrthopaedic Surgical Instruments,” which was filed on Sep. 30, 2007 byLuke Aram et al., each of these applications is assigned to the sameassignee as the present application, and each of which is herebyincorporated by reference.

CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATIONS

Cross-reference is made to co-pending U.S. Utility patent applicationSer. Nos. 12/240,985; 12/240,990; 12/240,988; 12/240,992; 12/240,994;12/240,996; 12/240,997; 12/240,998; 12/241,006; 12/241,002; 12/241,001;and 12/240,999. Each of these applications was filed on Sep. 29, 2008,and is assigned to the same assignee as the present application. Each ofthese applications is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to customized patient-specificorthopaedic surgical instruments and to methods, devices, and systemsfor fabricating and positioning such instruments.

BACKGROUND

Joint arthroplasty is a well-known surgical procedure by which adiseased and/or damaged natural joint is replaced by a prosthetic joint.A typical knee prosthesis includes a tibial tray, a femoral component, apolymer insert or bearing positioned between the tibial tray and thefemoral component, and, in some cases, a polymer patella button. Tofacilitate the replacement of the natural joint with the kneeprosthesis, orthopaedic surgeons use a variety of orthopaedic surgicalinstruments such as, for example, cutting blocks, drill guides, millingguides, and other surgical instruments. Typically, the orthopaedicsurgical instruments are generic with respect to the patient such thatthe same orthopaedic surgical instrument may be used on a number ofdifferent patients during similar orthopaedic surgical procedures.

SUMMARY

According to one aspect, a customized patient-specific tibial cuttingblock includes a body having a bone-facing surface that has a customizedpatient-specific negative contour configured to receive a portion of ananterior side of a patient's tibia that has a corresponding positivecontour. The customized patient-specific negative contour of the bodyincludes a first prominence positioned to contact the portion of theanterior side of the patient's tibia when the portion of the anteriorside of the patient's tibia is received in the customizedpatient-specific negative contour of the body. The customizedpatient-specific tibial cutting block also includes a first tabextending posteriorly from the body. The first tab has a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a first portion of the proximal side of thepatient's tibia that has a corresponding positive contour. Thecustomized patient-specific negative contour of the first tab includes asecond prominence positioned to contact the first portion of theproximal side of the patient's tibia when the first portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the first tab. The customizedpatient-specific tibial cutting block further includes a second tabextending posteriorly from the body. The second tab has a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a second portion of the proximal side of thepatient's tibia that has a corresponding positive contour. Thecustomized patient-specific negative contour of the second tab includesa third prominence positioned to contact the second portion of theproximal side of the patient's tibia when the second portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the second tab. The firstprominence is located anteriorly and inferiorly to both the secondprominence and the third prominence.

The first tab and the second tab may define an opening therebetween.

The body of the customized patient-specific tibial cutting block mayhave a cutting slot defined therein to allow a surgeon to perform aproximal cut on the patient's tibia using the cutting slot.

The customized patient-specific tibial cutting block may also includes acutting guide coupled to the body. The cutting guide has a cutting slotdefined therein. The cutting guide may be formed from a materialdifferent from the body and positioned to allow a surgeon to perform aproximal cut on the patient's tibia using the cutting slot.

The cutting guide may be located superiorly relative to the firstprominence.

The cutting guide may be formed from a metallic material and isovermolded to the body of the customized patient-specific femoralcutting block.

When viewed from the posterior direction, a V-shaped imaginary lineconnects the second prominence to the first prominence and the firstprominence to the third prominence.

When viewed from the superior direction, a V-shaped imaginary lineconnects the second prominence to the first prominence and the firstprominence to the third prominence.

The second and third prominences include protrusions positioned tocontact the articular surfaces of the proximal side of the patient'stibia when the proximal side of the patient's tibia is received in therespective customized patient-specific negative contours of the firstand second tabs.

According to another aspect, a customized patient-specific tibialcutting block includes a body having a bone-facing surface that has acustomized patient-specific negative contour configured to receive aportion of an anterior side of a patient's tibia that has acorresponding positive contour. The customized patient-specific negativecontour of the body includes a first prominence positioned to contactthe portion of the anterior side of the patient's tibia when the portionof the anterior side of the patient's tibia is received in thecustomized patient-specific negative contour of the body. The customizedpatient-specific tibial cutting block also includes a metallic cuttingguide overmolded to the body. The cutting guide has a cutting slotdefined therein. The customized patient-specific tibial cutting blockalso includes a first tab extending posteriorly from the body. The firsttab has a bone-facing surface that has a customized patient-specificnegative contour configured to receive a first portion of the proximalside of the patient's tibia that has a corresponding positive contour.The customized patient-specific negative contour of the first tabincludes a second prominence positioned to contact the first portion ofthe proximal side of the patient's tibia when the first portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the first tab. The customizedpatient-specific tibial cutting block further includes a second tabextending posteriorly from the body. The second tab has a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a second portion of the proximal side of thepatient's tibia that has a corresponding positive contour. Thecustomized patient-specific negative contour of the second tab includesa third prominence positioned to contact the second portion of theproximal side of the patient's tibia when the second portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the second tab. The firstprominence is located anteriorly and inferiorly to both the secondprominence and the third prominence. The first prominence is alsolocated inferiorly to the cutting slot of the cutting guide.

The first tab and the second tab may define an opening therebetween.

When viewed from the posterior direction, a V-shaped imaginary lineconnects the second prominence to the first prominence and the firstprominence to the third prominence.

When viewed from the superior direction, a V-shaped imaginary lineconnects the second prominence to the first prominence and the firstprominence to the third prominence.

The second and third prominences include protrusions positioned tocontact the articular surfaces of the proximal side of the patient'stibia when the proximal side of the patient's tibia is received in therespective customized patient-specific negative contours of the firstand second tabs.

According to one aspect, a customized patient-specific tibial cuttingblock includes a body having a bone-facing surface that has a customizedpatient-specific negative contour configured to receive a portion of ananterior side of a patient's tibia that has a corresponding positivecontour. The customized patient-specific negative contour of the bodyincludes a first prominence positioned to contact the portion of theanterior side of the patient's tibia when the portion of the anteriorside of the patient's tibia is received in the customizedpatient-specific negative contour of the body. The customizedpatient-specific tibial cutting block also includes a first tabextending posteriorly from the body. The first tab has a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a first portion of the proximal side of thepatient's tibia that has a corresponding positive contour. Thecustomized patient-specific negative contour of the first tab includes asecond prominence positioned to contact the first portion of theproximal side of the patient's tibia when the first portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the first tab. The customizedpatient-specific tibial cutting block further includes a second tabextending posteriorly from the body. The second tab has a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a second portion of the proximal side of thepatient's tibia that has a corresponding positive contour. Thecustomized patient-specific negative contour of the second tab includesa third prominence positioned to contact the second portion of theproximal side of the patient's tibia when the second portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the second tab. When viewed fromthe posterior direction, a V-shaped imaginary line connects the secondprominence to the first prominence and the first prominence to the thirdprominence. When viewed from the superior direction, a V-shapedimaginary line connects the second prominence to the first prominenceand the first prominence to the third prominence.

The first tab and the second tab may define an opening therebetween.

The body of the customized patient-specific tibial cutting block mayhave a cutting slot defined therein to allow a surgeon to perform aproximal cut on the patient's tibia using the cutting slot.

The customized patient-specific tibial cutting block may also includes acutting guide coupled to the body. The cutting guide has a cutting slotdefined therein. The cutting guide may be formed from a materialdifferent from the body and positioned to allow a surgeon to perform aproximal cut on the patient's tibia using the cutting slot.

The cutting guide may be located superiorly relative to the firstprominence.

The cutting guide may be formed from a metallic material and isovermolded to the body of the customized patient-specific femoralcutting block.

The second and third prominences include protrusions positioned tocontact the articular surfaces of the proximal side of the patient'stibia when the proximal side of the patient's tibia is received in therespective customized patient-specific negative contours of the firstand second tabs.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures,in which:

FIG. 1 is a simplified flow diagram of an algorithm for designing andfabricating a customized patient-specific orthopaedic surgicalinstrument;

FIG. 2 is a simplified flow diagram of a method for generating a modelof a patient-specific orthopaedic instrument;

FIG. 3 is a simplified flow diagram of a method for scaling a referencecontour;

FIGS. 4-6 are three-dimensional model's of a patient's tibia;

FIG. 7-9 are three-dimensional models of a patient's femur;

FIG. 10 is an anterior elevation an embodiment of a customizedpatient-specific orthopaedic surgical instrument;

FIG. 11 is a top plan view of the customized patient-specificorthopaedic surgical instrument of FIG. 10;

FIG. 12 is side elevation view of the customized patient-specificorthopaedic surgical instrument of FIG. 10;

FIG. 13 shows the customized patient-specific orthopaedic surgicalinstrument of FIG. 10, as viewed from the posterior direction; and

FIG. 14 shows the customized patient-specific orthopaedic surgicalinstrument of FIG. 10 secured to the tibia of a patient, as viewed fromthe superior direction.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

Terms representing anatomical references, such as anterior, posterior,medial, lateral, superior, inferior, etcetera, may be used throughoutthis disclosure in reference to the orthopaedic implants and instrumentsdescribed herein, along with a patient's natural anatomy. Such termshave well-understood meanings in both the study of anatomy and the fieldof orthopaedics. Use of such anatomical reference terms in thespecification and claims is intended to be consistent with theirwell-understood meanings unless noted otherwise.

Referring to FIG. 1, an algorithm 10 for fabricating a customizedpatient-specific orthopaedic surgical instrument is illustrated. What ismeant herein by the term “customized patient-specific orthopaedicsurgical instrument” is a surgical tool for use by a surgeon inperforming an orthopaedic surgical procedure that is intended, andconfigured, for use on a particular patient. As such, it should beappreciated that, as used herein, the term “customized patient-specificorthopaedic surgical instrument” is distinct from standard, non-patientspecific orthopaedic surgical instruments that are intended for use on avariety of different patients. Additionally, it should be appreciatedthat, as used herein, the term “customized patient-specific orthopaedicsurgical instrument” is distinct from orthopaedic prostheses, whetherpatient-specific or generic, which are surgically implanted in the bodyof the patient. Rather, customized patient-specific orthopaedic surgicalinstruments are used by an orthopaedic surgeon to assist in theimplantation of orthopaedic prostheses.

In some embodiments, the customized patient-specific orthopaedicsurgical instrument may be customized to the particular patient based onthe location at which the instrument is to be coupled to one or morebones of the patient, such as the femur and/or tibia. For example, insome embodiments, the customized patient-specific orthopaedic surgicalinstrument may include a bone-contacting or facing surface having anegative contour that matches or substantially matches the contour of aportion of the relevant bone of the patient. As such, the customizedpatient-specific orthopaedic surgical instrument is configured to becoupled to the bone of a patient in a unique location and position withrespect to the patient's bone. That is, the negative contour of thebone-contacting surface is configured to receive the matching contoursurface of the portion of the patient's bone. As such, the orthopaedicsurgeon's guesswork and/or intra-operative decision-making with respectto the placement of the orthopaedic surgical instrument are reduced. Forexample, the orthopaedic surgeon may not be required to locate landmarksof the patient's bone to facilitate the placement of the orthopaedicsurgical instrument, which typically requires some amount of estimationon part of the surgeon. Rather, the orthopaedic surgeon may simplycouple the customized patient-specific orthopaedic surgical instrumenton the bone or bones of the patient in the unique location. When socoupled, the cutting plane, drilling holes, milling holes, and/or otherguides are defined in the proper location relative to the bone andintended orthopaedic prosthesis. The customized patient-specificorthopaedic surgical instrument may be embodied as any type oforthopaedic surgical instrument such as, for example, a bone-cuttingblock, a drilling guide, a milling guide, or other type of orthopaedicsurgical instrument configured to be coupled to a bone of a patient.

As shown in FIG. 1, the algorithm 10 includes process steps 12 and 14,in which an orthopaedic surgeon performs pre-operative planning of theorthopaedic surgical procedure to be performed on a patient. The processsteps 12 and 14 may be performed in any order or contemporaneously witheach other. In process step 12, a number of medical images of therelevant bony anatomy or joint of the patient are generated. To do so,the orthopaedic surgeon or other healthcare provider may operate animaging system to generate the medical images. The medical images may beembodied as any number and type of medical images capable of being usedto generate a three-dimensional rendered model of the patient's bonyanatomy or relevant joint. For example, the medical images may beembodied as any number of computed tomography (CT) images, magneticresonance imaging (MRI) images, or other three-dimensional medicalimages. Additionally or alternatively, as discussed in more detail belowin regard to process step 18, the medical images may be embodied as anumber of X-ray images or other two-dimensional images from which athree-dimensional rendered model of the patient's relevant bony anatomymay be generated. Additionally, in some embodiments, the medical imagemay be enhanced with a contrast agent designed to highlight thecartilage surface of the patient's knee joint.

In process step 14, the orthopaedic surgeon may determine any additionalpre-operative constraint data. The constraint data may be based on theorthopaedic surgeon's preferences, preferences of the patient,anatomical aspects of the patient, guidelines established by thehealthcare facility, or the like. For example, the constraint data mayinclude the orthopaedic surgeon's preference for a metal-on-metalinterface, amount of inclination for implantation, the thickness of thebone to resect, size range of the orthopaedic implant, and/or the like.In some embodiments, the orthopaedic surgeon's preferences are saved asa surgeon's profile, which may used as a default constraint values forfurther surgical plans.

In process step 16, the medical images and the constraint data, if any,are transmitted or otherwise provided to an orthopaedic surgicalinstrument vendor or manufacturer. The medical images and the constraintdata may be transmitted to the vendor via electronic means such as anetwork or the like. After the vendor has received the medical imagesand the constraint data, the vendor processes the images in step 18. Theorthopaedic surgical instrument vendor or manufacturer process themedical images to facilitate the determination of the bone cuttingplanes, implant sizing, and fabrication of the customizedpatient-specific orthopaedic surgical instrument as discussed in moredetail below. For example, in process step 20 the vendor may convert orotherwise generate three-dimensional images from the medical images. Forexample, in embodiments wherein the medical images are embodied as anumber of two-dimensional images, the vendor may use a suitable computeralgorithm to generate one or more three-dimensional images form thenumber of two-dimensional images. Additionally, in some embodiments, themedical images may be generated based on an established standard such asthe Digital Imaging and Communications in Medicine (DICOM) standard. Insuch embodiments, an edge-detection, thresholding, watershead, orshape-matching algorithm may be used to convert or reconstruct images toa format acceptable in a computer aided design application or otherimage processing application. Further, in some embodiments, an algorithmmay be used to account for tissue such as cartilage not discernable inthe generated medical images. In such embodiments, any three-dimensionalmodel of the patient-specific instrument (see, e.g., process step 26below) may be modified according to such algorithm to increase the fitand function of the instrument.

In process step 22, the vendor may process the medical images, and/orthe converted/reconstructed images from process step 20, to determine anumber of aspects related to the bony anatomy of the patient such as theanatomical axis of the patient's bones, the mechanical axis of thepatient's bone, other axes and various landmarks, and/or other aspectsof the patient's bony anatomy. To do so, the vendor may use any suitablealgorithm to process the images.

In process step 24, the cutting planes of the patient's bone aredetermined. The planned cutting planes are determined based on the type,size, and position of the orthopaedic prosthesis to be used during theorthopaedic surgical procedure, on the process images such as specificlandmarks identified in the images, and on the constraint data suppliedby the orthopaedic surgeon in process steps 14 and 16. The type and/orsize of the orthopaedic prosthesis may be determined based on thepatient's anatomy and the constraint data. For example, the constraintdata may dictate the type, make, model, size, or other characteristic ofthe orthopaedic prosthesis. The selection of the orthopaedic prosthesismay also be modified based on the medical images such that anorthopaedic prosthesis that is usable with the bony anatomy of thepatient and that matches the constraint data or preferences of theorthopaedic surgeon is selected.

In addition to the type and size of the orthopaedic prosthesis, theplanned location and position of the orthopaedic prosthesis relative tothe patient's bony anatomy is determined. To do so, a digital templateof the selected orthopaedic prosthesis may be overlaid onto one or moreof the processed medical images. The vendor may use any suitablealgorithm to determine a recommended location and orientation of theorthopaedic prosthesis (i.e., the digital template) with respect to thepatient's bone based on the processed medical images (e.g., landmarks ofthe patient's bone defined in the images) and/or the constraint data.Additionally, any one or more other aspects of the patient's bonyanatomy may be used to determine the proper positioning of the digitaltemplate.

In some embodiments, the digital template along with surgical alignmentparameters may be presented to the orthopaedic surgeon for approval. Theapproval document may include the implant's rotation with respect tobony landmarks such as the femoral epicondyle, posterior condyles,sulcus groove (Whiteside's line), and the mechanical axis as defined bythe hip, knee, and/or ankle centers.

The planned cutting planes for the patient's bone(s) may then bedetermined based on the determined size, location, and orientation ofthe orthopaedic prosthesis. In addition, other aspects of the patient'sbony anatomy, as determined in process step 22, may be used to determineor adjust the planned cutting planes. For example, the determinedmechanical axis, landmarks, and/or other determined aspects of therelevant bones of the patient may be used to determine the plannedcutting planes.

In process step 26, a model of the customized patient-specificorthopaedic surgical instrument is generated. In some embodiments, themodel is embodied as a three-dimensional rendering of the customizedpatient-specific orthopaedic surgical instrument. In other embodiments,the model may be embodied as a mock-up or fast prototype of thecustomized patient-specific orthopaedic surgical instrument. Theparticular type of orthopaedic surgical instrument to be modeled andfabricated may be determined based on the orthopaedic surgical procedureto be performed, the constraint data, and/or the type of orthopaedicprosthesis to be implanted in the patient. As such, the customizedpatient-specific orthopaedic surgical instrument may be embodied as anytype of orthopaedic surgical instrument for use in the performance of anorthopaedic surgical procedure. For example, the orthopaedic surgicalinstrument may be embodied as a bone-cutting block, a drilling guide, amilling guide, and/or any other type of orthopaedic surgical tool orinstrument.

The particular shape of the customized patient-specific orthopaedicsurgical instrument is determined based on the planned location of theorthopaedic surgical instrument relative to the patient's bony anatomy.The location of the customized patient-specific orthopaedic surgicalinstrument with respect to the patient's bony anatomy is determinedbased on the type and determined location of the orthopaedic prosthesisto be used during the orthopaedic surgical procedure. That is, theplanned location of the customized patient-specific orthopaedic surgicalinstrument relative to the patient's bony anatomy may be selected basedon, in part, the planned cutting planes of the patient's bone(s) asdetermined in step 24. For example, in embodiments wherein thecustomized patient-specific orthopaedic surgical instrument is embodiedas a bone-cutting block, the location of the orthopaedic surgicalinstrument is selected such that the cutting guide of the bone-cuttingblock matches one or more of the planned cutting planes determined inprocess step 24. Additionally, the planned location of the orthopaedicsurgical instrument may be based on the identified landmarks of thepatient's bone identified in process step 22.

In some embodiments, the particular shape or configuration of thecustomized patient-specific orthopaedic surgical instrument may bedetermined based on the planned location of the instrument relative tothe patient's bony anatomy. That is, the customized patient-specificorthopaedic surgical instrument may include a bone-contacting surfacehaving a negative contour that matches the contour of a portion of thebony anatomy of the patient such that the orthopaedic surgicalinstrument may be coupled to the bony anatomy of the patient in a uniquelocation, which corresponds to the pre-planned location for theinstrument. When the orthopaedic surgical instrument is coupled to thepatient's bony anatomy in the unique location, one or more guides (e.g.,cutting or drilling guide) of the orthopaedic surgical instrument may bealigned to one or more of the bone cutting plane(s) as discussed above.

One illustrative embodiment of a method 40 for generating a model, suchas a computer model, of a patient-specific orthopaedic instrument isillustrated in FIGS. 2 through 9. The method 40 begins with a step 42 inwhich a cartilage thickness value is determined. The cartilage thicknessvalue is indicative of the average thickness of the cartilage of thepatient's bone. As such, in one embodiment, the cartilage thicknessvalue is equal to the average thickness of cartilage for an individualhaving similar characteristics as the patient. For example, thecartilage thickness value may be equal to the average thickness value ofindividuals of the same gender as the patient, the same age as thepatient, having the same activity level of the patient, and/or the like.In other embodiments, the cartilage thickness value is determined basedon one or more medical images of the patient's bone, such as thoseimages transmitted in process step 16.

In step 44, a reference contour of the patient's relevant bone isdetermined. The reference contour is based on the surface contour of athree-dimensional model of the patient's relevant bone, such as thethree-dimensional model generated in step 20. Initially the referencecontour is identical to a region (i.e. the region of interest such asthe distal end of the patient's femur or the proximal end of thepatient's tibia) of the patient's bone. That is, in some embodiments,the reference contour is juxtaposed on the surface contour of the regionof the patient's bone.

Subsequently, in step 46, the reference contour is scaled to compensatefor the cartilage thickness value determined in step 42. To do so, inone embodiment, the scale of the reference contour is increased based onthe cartilage thickness value. For example, the scale of the referencecontour may be increased by an amount equal to or determined from thecartilage thickness value. However, in other embodiments, the referencecontour may be scaled using other techniques designed to scale thereference contour to a size at which the reference contour iscompensated for the thickness of the cartilage on the patient's bone.

For example, in one particular embodiment, the reference contour isscaled by increasing the distance between a fixed reference point and apoint lying on, and defining in part, the reference contour. To do so,in one embodiment, a method 60 for scaling a reference contour asillustrated in FIG. 3 may be used. The method 60 begins with step 62 inwhich a medial/lateral line segment is established on thethree-dimensional model of the patient's relevant bone. Themedial/lateral line segment is defined or otherwise selected so as toextend from a point lying on the medial surface of the patient's bone toa point lying on lateral surface of the patient's bone. The medialsurface point and the lateral surface point may be selected so as todefine the substantially maximum local medial/lateral width of thepatient's bone in some embodiments.

In step 64, an anterior/posterior line segment is established on thethree-dimensional model of the patient's relevant bone. Theanterior/posterior line segment is defined or otherwise selected so asto extend from a point lying on the anterior surface of the patient'sbone to a point lying on posterior surface of the patient's bone. Theanterior surface point and the posterior surface point may be selectedso as to define the substantially maximum local anterior/posterior widthof the patient's bone in some embodiments.

The reference point from which the reference contour will be scaled isdefined in step 66 as the intersection point of the medial/lateral linesegment and anterior/posterior line segment. As such, it should beappreciated that the medial surface point, the lateral surface point,the anterior surface point, and the posterior surface point lie on thesame plane. After the reference point is initially established in step66, the reference point is moved or otherwise translated toward an endof the patient's bone. For example, in embodiments wherein the patient'sbone is embodied as a femur, the reference point is moved inferiorlytoward the distal end of the patient's femur. Conversely, in embodimentswhen the patient's bone is embodied as a tibia, the reference point ismoved superiorly toward the proximal end of the patient's tibia. In oneembodiment, the reference point is moved a distance equal to about halfthe length of the anterior/posterior line segment as determined in step64. However, in other embodiments, the reference point may be movedother distances sufficient to compensate the reference contour forthickness of the cartilage present on the patient's bone.

Once the location of the reference point has been determined in step 68,the distance between the reference point and each point lying on, anddefining in part, the reference contour is increased in step 70. To doso, in one particular embodiment, each point of the reference contour ismoved a distance away from the reference point based on a percentagevalue of the original distance defined between the reference point andthe particular point on the reference contour. For example, in oneembodiment, each point lying on, and defining in part, the referencecontour is moved away from the reference point in by a distance equal toa percentage value of the original distance between the reference pointand the particular point. In one embodiment, the percentage value is inthe range of about 5 percent to about thirty percent. In one particularembodiment, the percentage value is about ten percent.

Referring now to FIGS. 4-9, in another embodiment, the reference contouris scaled by manually selecting a local “high” point on the surfacecontour of the three-dimensional image of the patient's bone. Forexample, in embodiments wherein the relevant patient's bone is embodiedas a tibia as illustrated in FIGS. 4-6, the reference point 90 isinitially located on the tibial plateau high point of the tibial model92. Either side of the tibial plateau may be used. Once the referencepoint 90 is initially established on the tibial plateau high point, thereference point 90 is translated to the approximate center of theplateau as illustrated in FIG. 5 such that the Z-axis defining thereference point is parallel to the mechanical axis of the tibial model92. Subsequently, as illustrated in FIG. 6, the reference point is movedin the distal direction by a predetermined amount. In one particularembodiment, the reference point is moved is the distal direction byabout 20 millimeters, but other distances may be used in otherembodiments. For example, the distance over which the reference point ismoved may be based on the cartilage thickness value in some embodiments.

Conversely, in embodiments wherein the relevant patient's bone isembodied as a femur as illustrated in FIGS. 7-9, the reference point 90is initially located on the most distal point of the distal end of thefemoral model 94. Either condyle of the femoral model 94 may be used invarious embodiments. Once the reference point 90 is initiallyestablished on the most distal point, the reference point 90 istranslated to the approximate center of the distal end of the femoralmodel 94 as illustrated in FIG. 8 such that the Z-axis defining thereference point 90 is parallel to the mechanical axis of the femoralmodel 92. The anterior-posterior width 96 of the distal end of thefemoral model 94 is also determined. Subsequently, as illustrated inFIG. 9, the reference point is moved or otherwise translated in theproximal or superior direction by a distance 98. In one particularembodiment, the reference point is moved in the distal or superiordirection by a distance 98 equal to about half the distance 96. As such,it should be appreciated that one of a number of different techniquesmay be used to define the location of the reference point based on, forexample, the type of bone.

Referring now back to FIG. 2, once the reference contour has been scaledin step 46, the medial/lateral sides of the reference contour areadjusted in step 48. To do so, in one embodiment, the distance betweenthe reference point and each point lying on, and defining in part, themedial side and lateral side of the reference contour is decreased. Forexample, in some embodiments, the distance between the reference pointand the points on the medial and lateral sides of the scaled referencecontour are decreased to the original distance between such points. Assuch, it should be appreciated that the reference contour is offset orotherwise enlarged with respect to the anterior side of the patient'sbone and substantially matches or is otherwise not scaled with respectto the medial and lateral sides of the patient's bone.

The reference contour may also be adjusted in step 48 for areas of thepatient's bone having a reduced thickness of cartilage. Such areas ofreduced cartilage thickness may be determined based on the existence ofbone-on-bone contact as identified in a medical image, simulation, orthe like. Additionally, information indicative of such areas may beprovided by the orthopaedic surgeon based on his/her expertise. If oneor more areas of reduced cartilage thickness are identified, thereference contour corresponding to such areas of the patient's bone isreduced (i.e., scaled back or down).

Additionally, in some embodiments, one or more osteophytes on thepatient's bone may be identified; and the reference contour may becompensated for such presence of the osteophytes. By compensating forsuch osteophytes, the reference contour more closely matches the surfacecontour of the patient's bone. Further, in some embodiments, a distalend (in embodiments wherein the patient's bone is embodied as a tibia)or a proximal end (in embodiments wherein the patient's bone is embodiedas a femur) of the reference contour may be adjusted to increase theconformity of the reference contour to the surface contour of the bone.For example, in embodiments wherein the patient's bone is a femur, thesuperior end of the scaled reference contour may be reduced or otherwisemoved closer to the surface contour of the patient's femur in the regionlocated superiorly to a cartilage demarcation line defined on thepatient's femur. Conversely, in embodiments wherein the patient's boneis embodied as a tibia, an inferior end of the scaled reference contourmay be reduced or otherwise moved closer to the surface contour of thepatient's tibia in the region located inferiorly to a cartilagedemarcation line of the patient's tibia. As such, it should beappreciated that the scaled reference contour is initially enlarged tocompensate for the thickness of the patient's cartilage on the patient'sbone. Portions of the scaled reference contour are then reduced orotherwise moved back to original positions and/or toward the referencepoint in those areas where cartilage is lacking, reduced, or otherwisenot present.

Once the reference contour has been scaled and adjusted in steps 46 and48, the position of the cutting guide is defined in step 50. Inparticular, the position of the cutting guide is defined based on anangle defined between a mechanical axis of the patient's femur and amechanical axis of the patient's tibia. The angle may be determined byestablishing a line segment or ray originating from the proximal end ofthe patient's femur to the distal end of the patient's femur anddefining a second line segment or ray extending from the patient's anklethrough the proximal end of the patient's tibia. The angle defined bythese two line segments/rays is equal to the angle defined between themechanical axis of the patient's femur and tibia. The position of thebone cutting guide is then determined based on the angle between themechanical axes of the patient's femur and tibia. It should beappreciated that the position of the cutting guide defines the positionand orientation of the cutting plane of the customized patient-specificcutting block. Subsequently, in step 52, a negative contour of thecustomized patient-specific cutting block is defined based on the scaledand adjusted reference contour and the angle defined between themechanical axis of the femur and tibia.

Referring back to FIG. 1, after the model of the customizedpatient-specific orthopaedic surgical instrument has been generated inprocess step 26, the model is validated in process step 28. The modelmay be validated by, for example, analyzing the rendered model whilecoupled to the three-dimensional model of the patient's anatomy toverify the correlation of cutting guides and planes, drilling guides andplanned drill points, and/or the like. Additionally, the model may bevalidated by transmitting or otherwise providing the model generated instep 26 to the orthopaedic surgeon for review. For example, inembodiments wherein the model is a three-dimensional rendered model, themodel along with the three-dimensional images of the patient's relevantbone(s) may be transmitted to the surgeon for review. In embodimentswherein the model is a physical prototype, the model may be shipped tothe orthopaedic surgeon for validation.

After the model has been validated in process step 28, the customizedpatient-specific orthopaedic surgical instrument is fabricated inprocess step 30. The customized patient-specific orthopaedic surgicalinstrument may be fabricated using any suitable fabrication device andmethod. Additionally, the customized patient-specific orthopaedicinstrument may be formed from any suitable material such as a metallicmaterial, a plastic material, or combination thereof depending on, forexample, the intended use of the instrument. The fabricated customizedpatient-specific orthopaedic instrument is subsequently shipped orotherwise provided to the orthopaedic surgeon. The surgeon performs theorthopaedic surgical procedure in process step 32 using the customizedpatient-specific orthopaedic surgical instrument. As discussed above,because the orthopaedic surgeon does not need to determine the properlocation of the orthopaedic surgical instrument intra-operatively, whichtypically requires some amount of estimation on part of the surgeon, theguesswork and/or intra-operative decision-making on part of theorthopaedic surgeon is reduced.

Referring now to FIGS. 10-12, in one embodiment, the customizedpatient-specific orthopaedic surgical instrument may be embodied as atibial cutting block 100. The cutting block 100 is configured to becoupled to a tibia of a patient. The cutting block 100 includes a body102 configured to be coupled to the anterior side of the patient's tibiaand two arms or tabs 104, 106 which extend posteriorly away from thebody 102. The tabs 104, 106 are configured to wrap around a proximal endof the tibia as discussed in more detail below. The cutting block 100may be formed from any suitable material. For example, the cutting block100 may be formed from a plastic or resin material. In one particularembodiment, the cutting block 100 is formed from Vero resin using arapid prototype fabrication process. However, the cutting block 100 maybe formed from other materials in other embodiments. For example, inanother particular embodiment, the cutting block 100 is formed from apolyimide thermoplastic resin, such as a Ultem resin, which iscommercially available from Saudi Basic Industries CorporationInnovative Plastics of Riyhadh, Saudi Arabia.

The body 102 includes a bone-contacting or bone-facing surface 112 andan outer surface 114 opposite the bone-facing surface 112. The outersurface 114 includes a number of guide holes or passageways 116 definedtherethrough. A guide pin bushing 118 is received in each guide hole116. The guide pin bushings 118 include an internal passageway 120 sizedto receive a respective guide pin to secure the block 100 to thepatient's tibia. As shown in FIG. 12, the guide passageways 116 extendsfrom the outer surface 114 to the bone-facing surface 112 and iscounterbored on the bone-facing surface 112. That is, the passageway 116has an opening 122 on the bone-facing surface 112 having a diametergreater than the diameter of an opening 124 on the outer surface 114

The cutting guide 100 includes a cutting guide 130 secured to the body102. In one particular embodiment, the cutting guide 130 is overmoldedto the body 102. The cutting guide 130 includes a cutting guide slot132. The cutting guide 130 may be formed from the same material as thebody 102 or from a different material. In one particular embodiment, thecutting guide 130 is formed from a metallic material such as stainlesssteel. The body 102 also includes a window or opening 134 to allow asurgeon to visualize the positioning of the block 100 on the patient'stibia by viewing portions of the tibia through the opening 134. In theillustrative embodiment, the window 134 is embodied as a notch 136defined on a superior end surface 137 of the body 102 of the cuttingguide 100. However, in other embodiments, the cutting block 100 mayinclude windows or openings formed in the body 102 having other shapesand sizes.

The bone-facing surface 112 of the body 102 includes a negative contour138 configured to receive a portion of the anterior side of thepatient's tibia having a corresponding contour and a portion of themedial side of the patient's tibia. The customized patient-specificnegative contour 138 of the bone-contacting surface 112 allows thepositioning of the cutting block 100 on the patient's tibia in a uniquepre-determined location and orientation. In the exemplary embodimentdescribed herein, the negative contour 138 is selected such that cuttingblock 100 is configured to be coupled to the patient's tibia on ananterior-medial side, as opposed to solely on the anterior surface ofthe tibia. For example, as illustrated in FIG. 11, when the cuttingblock 100 is secured to a patient's tibia, an angle (α) is definedbetween a vertically-extending, bisecting plane 162 of the body 102 ofthe block 100 and a bisecting sagittal plane 164 of the patient's tibia(i.e., the A/P plane 164). The magnitude of the angle (α) may beselected based on, for example, the gender or age of the patient. In oneparticular embodiment, the angle (α) is in the range of about 10° toabout 30°. In another particular embodiment, the angle is about 20°.

The tabs 104, 106 include a bone-contacting or bone-facing surface 140,142, respectively, and an outer surface 144, 146, respectively, oppositethe bone-facing surface 140, 142. The bone-facing surface 140 of the tab104 includes a negative contour 148 configured to receive a portion ofthe proximal side of the patient's tibia having a respectivecorresponding contour. Similarly, the bone-facing surface 142 of the tab106 includes a negative contour 150 configured to receive a portion ofthe proximal side of the patient's tibia having a respectivecorresponding contour.

As can be seen in FIG. 13. the negative contour 138 of the body 102includes an anterior prominence 172. The anterior prominence 172 abutsthe anterior bone surface of the proximal tibia when the tibial cuttingblock 100 is properly positioned on the proximal tibia. The negativecontours of each of the tabs 104, 106 likewise has a prominence formedthereon. In particular, the negative contour 148 of the tab 104 has aprotrusion 174 that is positioned to contact a portion of the articularsurface of the proximal side of the patient's tibia when the cuttingblock 100 is secured thereto (see FIG. 14). Similarly, the negativecontour 150 of the tab 106 has a protrusion 176 that is positioned tocontact a portion of the articular surface of the proximal side of thepatient's tibia when the cutting block 100 is secured thereto (see FIG.14).

As can be seen in FIGS. 13 and 14, the anterior prominence 172 islocated anteriorly and inferiorly relative to the prominences 174, 176.As such, when viewed from the posterior direction such as shown in FIG.13, a V-shaped imaginary line 178 connects the prominence 174 of the tab104 to the anterior prominence 172, and the anterior prominence 172 tothe prominence 176 of the tab 106. Likewise, when viewed from thesuperior direction, a V-shaped imaginary line 180 connects theprominence 174 of the tab 104 to the anterior prominence 172, and theanterior prominence 172 to the prominence 176 of the tab 106. Such aconfiguration using the three prominences 172, 174, 176 enhances thestability of the cutting block 100.

It should be appreciated that the prominences 174, 176 may be designedto sit on top of the articular cartilage of the tibia. In addition, theprominences 174, 176 may be customed designed to sit withinpre-operatively determined voids in the cartilage in the mannerdescribed in co-pending, commonly-owned U.S. patent application Ser. No.______, entitled “Customized Patient-Specific Cutting Blocks HavingLocating Features and Method of Making the Same” by Bryan Rose et al.,which was filed concurrently herewith and is incorporated herein byreference.

As discussed above, the arms or tabs 104, 106 extend posteriorly fromthe body 102 to define a U-shaped opening 105 therebetween. The tabs104, 106 may extend from the body 102 the same distance or a differentdistance. For example, as shown in FIG. 11, the tab 104 extends from thebody 102 a distance 152 and the tab 106 extends from the body 102 by adistance 154, which is greater than the distance 152. Each of the tabs104, 106 includes a respective elongated opening or window 160 definedtherethrough. Similar to the window 134 described above, the windows 160allow a surgeon to visualize the positioning of the block 100 on thepatient's tibia by viewing portions of the proximal end tibia throughthe opening 160 134.

In some embodiments, the negative contours 138, 148, 150 of thebone-contacting surfaces 112, 140, 142 of the cutting block 1400 may ormay not match the corresponding contour surface of the patient's bone.That is, as discussed above, the negative contours 138, 148, 150 may bescaled or otherwise resized (e.g., enlarged) to compensate for thepatient's cartilage or lack thereof.

In use, the tibial cutting block 100 is coupled to the proximal end ofthe patient's tibia. Again, because the bone-contacting surfaces 112,140, 142 of the cutting block 100 include the negative contours 138,148, 150 the block 100 may be coupled to the patient's tibia in apre-planned, unique position. When so coupled, the tabs 104, 106 wraparound the proximal end of the patient's tibia and the lips 108, 110 ofthe tabs 104, 106 wrap around the posterior side of the patient's tibia.Additionally, when the block 100 is coupled to the patient's tibia, aportion of the anterior side of the tibia is received in the negativecontour 138 of the body 102 and a portion of the proximal side of thepatient's tibia is received in the negative contours 148, 150 of thetabs 104, 106.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only illustrative embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the disclosure are desired to be protected.

There are a plurality of advantages of the present disclosure arisingfrom the various features of the apparatus, system, and method describedherein. It will be noted that alternative embodiments of the apparatus,system, and method of the present disclosure may not include all of thefeatures described yet still benefit from at least some of theadvantages of such features. Those of ordinary skill in the art mayreadily devise their own implementations of the apparatus, system, andmethod that incorporate one or more of the features of the presentinvention and fall within the spirit and scope of the present disclosureas defined by the appended claims.

What is claimed is:
 1. A customized patient-specific tibial cuttingblock, comprising: a body having a bone-facing surface that has acustomized patient-specific negative contour configured to receive aportion of an anterior side of a patient's tibia that has acorresponding positive contour, the customized patient-specific negativecontour of the body comprises a first prominence positioned to contactthe portion of the anterior side of the patient's tibia when the portionof the anterior side of the patient's tibia is received in thecustomized patient-specific negative contour of the body, a first tabextending posteriorly from the body, the first tab having a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a first portion of the proximal side of thepatient's tibia that has a corresponding positive contour, thecustomized patient-specific negative contour of the first tab comprisesa second prominence positioned to contact the first portion of theproximal side of the patient's tibia when the first portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the first tab, and a second tabextending posteriorly from the body, the second tab having a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a second portion of the proximal side of thepatient's tibia that has a corresponding positive contour, thecustomized patient-specific negative contour of the second tab comprisesa third prominence positioned to contact the second portion of theproximal side of the patient's tibia when the second portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the second tab, wherein the firstprominence is located anteriorly and inferiorly to both the secondprominence and the third prominence.
 2. The customized patient-specifictibial cutting block of claim 1, wherein the first tab and the secondtab define an opening therebetween.
 3. The customized patient-specifictibial cutting block of claim 1, wherein the body has a cutting slotdefined therein, the cutting slot being positioned to allow a surgeon toperform a proximal cut on the patient's tibia using the cutting slot. 4.The customized patient-specific tibial cutting block of claim 1, furthercomprising a cutting guide coupled to the body, wherein: the cuttingguide has a cutting slot defined therein, and the cutting guide isformed from a material different from the body and being positioned toallow a surgeon to perform a proximal cut on the patient's tibia usingthe cutting slot.
 5. The customized patient-specific tibial cuttingblock of claim 4, wherein the cutting guide is formed from a metallicmaterial and is overmolded to the body of the customizedpatient-specific femoral cutting block.
 6. The customizedpatient-specific tibial cutting block of claim 1, wherein when viewedfrom the posterior direction, a V-shaped imaginary line connects thesecond prominence to the first prominence and the first prominence tothe third prominence.
 7. The customized patient-specific tibial cuttingblock of claim 1, wherein when viewed from the superior direction, aV-shaped imaginary line connects the second prominence to the firstprominence and the first prominence to the third prominence.
 8. Thecustomized patient-specific tibial cutting block of claim 1, wherein thesecond and third prominences comprises protrusions positioned to contactthe articular surfaces of the proximal side of the patient's tibia whenthe proximal side of the patient's tibia is received in the respectivecustomized patient-specific negative contours of the first and secondtabs.
 9. The customized patient-specific tibial cutting block of claim1, further comprising a cutting guide coupled to the body, wherein: thecutting guide has a cutting slot defined therein, and the cutting guideis located superiorly relative to the first prominence.
 10. A customizedpatient-specific tibial cutting block, comprising: a body having abone-facing surface that has a customized patient-specific negativecontour configured to receive a portion of an anterior side of apatient's tibia that has a corresponding positive contour, thecustomized patient-specific negative contour of the body comprises afirst prominence positioned to contact the portion of the anterior sideof the patient's tibia when the portion of the anterior side of thepatient's tibia is received in the customized patient-specific negativecontour of the body, a metallic cutting guide overmolded to the body,the cutting guide having a cutting slot defined therein, a first tabextending posteriorly from the body, the first tab having a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a first portion of the proximal side of thepatient's tibia that has a corresponding positive contour, thecustomized patient-specific negative contour of the first tab comprisesa second prominence positioned to contact the first portion of theproximal side of the patient's tibia when the first portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the first tab, and a second tabextending posteriorly from the body, the second tab having a bone-facingsurface that has a customized patient-specific negative contourconfigured to receive a second portion of the proximal side of thepatient's tibia that has a corresponding positive contour, thecustomized patient-specific negative contour of the second tab comprisesa third prominence positioned to contact the second portion of theproximal side of the patient's tibia when the second portion of theproximal side of the patient's tibia is received in the customizedpatient-specific negative contour of the second tab, wherein the firstprominence is located (i) anteriorly and inferiorly to both the secondprominence and the third prominence, and (ii) inferiorly to the cuttingslot of the cutting guide.
 11. The customized patient-specific tibialcutting block of claim 10, wherein the first tab and the second tabdefine an opening therebetween.
 12. The customized patient-specifictibial cutting block of claim 10, wherein when viewed from the posteriordirection, a V-shaped imaginary line connects the second prominence tothe first prominence and the first prominence to the third prominence.13. The customized patient-specific tibial cutting block of claim 10,wherein when viewed from the superior direction, a V-shaped imaginaryline connects the second prominence to the first prominence and thefirst prominence to the third prominence.
 14. The customizedpatient-specific tibial cutting block of claim 10, wherein the secondand third prominences comprises protrusions positioned to contact thearticular surfaces of the proximal side of the patient's tibia when theproximal side of the patient's tibia is received in the respectivecustomized patient-specific negative contours of the first and secondtabs.
 15. A customized patient-specific tibial cutting block,comprising: a body having a bone-facing surface that has a customizedpatient-specific negative contour configured to receive a portion of ananterior side of a patient's tibia that has a corresponding positivecontour, the customized patient-specific negative contour of the bodycomprises a first prominence positioned to contact the portion of theanterior side of the patient's tibia when the portion of the anteriorside of the patient's tibia is received in the customizedpatient-specific negative contour of the body, a first tab extendingposteriorly from the body, the first tab having a bone-facing surfacethat has a customized patient-specific negative contour configured toreceive a first portion of the proximal side of the patient's tibia thathas a corresponding positive contour, the customized patient-specificnegative contour of the first tab comprises a second prominencepositioned to contact the first portion of the proximal side of thepatient's tibia when the first portion of the proximal side of thepatient's tibia is received in the customized patient-specific negativecontour of the first tab, and a second tab extending posteriorly fromthe body, the second tab having a bone-facing surface that has acustomized patient-specific negative contour configured to receive asecond portion of the proximal side of the patient's tibia that has acorresponding positive contour, the customized patient-specific negativecontour of the second tab comprises a third prominence positioned tocontact the second portion of the proximal side of the patient's tibiawhen the second portion of the proximal side of the patient's tibia isreceived in the customized patient-specific negative contour of thesecond tab, wherein (i) when viewed from the posterior direction, afirst V-shaped imaginary line connects the second prominence to thefirst prominence and the first prominence to the third prominence, and(ii) when viewed from the superior direction, a V-shaped imaginary lineconnects the second prominence to the first prominence and the firstprominence to the third prominence.
 16. The customized patient-specifictibial cutting block of claim 15, wherein the first tab and the secondtab define an opening therebetween.
 17. The customized patient-specifictibial cutting block of claim 16, wherein the body has a cutting slotdefined therein, the cutting slot being positioned to allow a surgeon toperform a proximal cut on the patient's tibia using the cutting slot.18. The customized patient-specific tibial cutting block of claim 15,further comprising a cutting guide coupled to the body, wherein: thecutting guide has a cutting slot defined therein, and the cutting guideis formed from a material different from the body and being positionedto allow a surgeon to perform a proximal cut on the patient's tibiausing the cutting slot.
 19. The customized patient-specific tibialcutting block of claim 18, wherein the cutting guide is formed from ametallic material and is overmolded to the body of the customizedpatient-specific femoral cutting block.
 20. The customizedpatient-specific tibial cutting block of claim 15, wherein the secondand third prominences comprises protrusions positioned to contact thearticular surfaces of the proximal side of the patient's tibia when theproximal side of the patient's tibia is received in the respectivecustomized patient-specific negative contours of the first and secondtabs.